The invention concerns epoxy resin casting compounds based on polyepoxides, polycarboxylic acids and/or polycarboxylic acid anhydrides with directly or latently present carboxyl functions, which can be converted by polyaddition and/or polymerization into insoluble and unmeltable cross-linked polymer materials and which may optionally contain fillers and other additives.
It is known, and much effort has been spent, to prepare cross-linked polymers from castable mixtures of monomers or from castable mixtures of monomers and pre-polymers which contain polymerizable carbon double bonds as well as epoxy functions and components which can be added to them, such as, for instance, dicarboxylic acids or dicarboxylic acid anhydrides. It was essentially the aim of these efforts to create more economically processable and less expensive casting compounds than those purely on an epoxy resin polyadduct base. However, cross-linked polymers on the above-mentioned base have up to now not found any substantial technical application. The reasons for this are, the limitations of the processing technique, e.g., the relatively high vapor pressure of inexpensive polymerizable monomers such as styrene, vinyl toluol and methylmethacrylate; the relatively high viscosity of unsaturated prepolymers such as unsaturated polyester resins; the low rate of polymerization and the fact that allyl monomers can be only reacted completely under uneconomical reaction conditions (high temperature and a long reaction time); the low storage stability and poor control and management of the cross-linking reaction such as, for instance, in the case of monoallylitaconate; or because of excessive volume reduction during the cross-linking reaction. Other reasons for the infrequent technical application of the above-mentioned casting compounds are the level of their mechanical-thermal properties, which is lower than with epoxy casting compounds, and their usually lower chemical-thermal stability.
It is further known that adducts of maleic acid monoallyl esters to polyepoxy compounds with a low acid number and a low epoxy number can be converted by peroxide-initiated polymerization into thermally stable, cross-linked polymers, which are preferably suited as a resin matrix for composite materals (cf. German Offenlegungsschrift No. 2,205,925, page 3, paragraph 2, to page 4, paragraph 2).